A statement said, "Sadly the reports are true that Robin has contracted pneumonia and is in a coma. We are all hoping and praying that he will pull through. Because of this situation, Robin's website is temporarily unavailable. Sorry for any inconvenience."
Gibb's family is staying by his side in the hospital. Wife Dwina smiled and son Robin-John waved to photographers as they entered the central London hospital, reports the Press Association. Other family members, including brother Barry, 65, daughter Melissa, 37, and son Spencer, 39, also visited.
The Bee Gees star was diagnosed with colon and liver cancer last year, but it was thought to have been in remission.